EDEXCEL Biology Unit 2 6BIO2 21st May 2012

lol
Expect the best, Prepare for the worst. -Muhammad Ali Jinnah

i think its because people who did the exams in 09/10 didn't have many past papers to practice from.. Still though that shouldnt account for a 15% increase -_-

Anyone know why endemic species have low genetic diversity?

Anyone know why endemic species have low genetic diversity?

I already feel like I'm gonna fail so I haven't had any motivation whatsoever to revise

can any1 Explain the role of meiosis in the production of gametes and genetic variation through recombination of alleles and genes including independent assortment and crossing over

I have typed up all of the core practicals except the mineral ions one as this came up in january so is HIGHLY unlikely to come up again. But here you go
good luck for tomorrow:


Core Practical 1: Observing Mitosis:
Cut 5mm of a root tip off as this is where the totipotent cells are located that are undergoing mitosis. Add an orcein stain and an acid- the stain highlights the chromosomes and the acid softens the tissue. Using a cover slip, gently break open the cell and squash to spread the chromosomes out. Heat the stain in order to intensify the stain, and then observe the chromosomes under a microscope.
Core practical 2: Antimicrobial properties of Plant
Crush 3g of plant in a pestel and mortar to form a plant extract. Place the extract on a paper disc and then onto a sterile agar dish containing bacteria (control variable) Aseptic technique used. Repeat this with other plants and use a control (disc containing no plant extract). Tape lightly around the plate to allow for aerobic conditions and prevent the growth of harmful anaerobic bacteria. Incubate at 25 degrees for 24 hours. Measure the zone of inhibition (area of no bacteria growth). The larger the zone of inhibition, the better the antimicrobial properties.
Core Practical 3: Plant Fibres
Obtain fibres from different plants that have been retted for a week to allow for fibres to be easily obtained. Compare these with synthetic fibres obtained. Using fibres of the same length and the same diameter, attach either end of the fibre to a clamp. Add masses to the fibres and measure the weight required for the fibre to snap. Repeat this experiement three times with fibres from the same plant with the same storage and environmental conditions.
Core Practical 4:
Totipotency of cells.
Using a blade, cut up a cress into different sections ie. The roots, shoots, leaves etc. Using aceptic technique, disinfect the work surfaces with ethanoic acid and cotton wool to prevent the growth of harmful microbes. Once the cress is cut up, place the different sections of the cress into mccartney bottles containing a growth medium. ( the growth medium will act as a chemical stimulus leading to the stem cells becoming specialised if the section cut contains stem cell). Cover the mccartney bottle with cling film to prevent the loss of moisture and place under a light bank. Observe every 3 days for any changes. The cress cutting that has grown into a whole new plant will contain the totipotent cells.

Could anyone explain why genetic diversity is advantageous? As in more likely to survive, reproduce.

I wouldn't say the mineral ions is highly unlikely, because the enzyme experiment came up in the unit 1 paper in January and again in the Unit 1 exam we took last week, so I personally think we should also do the mineral ions experiment. Edexcel are Evil.

Could anyone explain why genetic diversity is advantageous? As in more likely to survive, reproduce.

genetic diversity is advantageous as should the conditions change, a greater genetic diversity means that organisms are likely to have the advantageous alleles to be able to survive and pass these alleles onto furture generations. However, if there is a low genetic diversity, it is unlikely that the species will survive a change in conditions, so is at risk from extinction.

This is why zoos are so keen to maintain and improve genetic diversity

as far as i know one reason is cause the immune system is more varied so the organism has a higher chance of surviving infection or whatever so can actually live to reproduce.

different characteristics can be expressed within a species and if these characteristics are more beneficial then they get passed on as the organism that had the characteristic mated more.

What on earth is 'spermatogenesis oogenesis???
I am in year 13 and am retaking this unit because A2 is just impossible and need all the marks I can get - but never heard of that!!